Pilot and main fuel gas supply means for pressurized gas-fired space heater

ABSTRACT

This invention provides novel means for supplying pilot and main fuel gas to the fuel gas-combustion air mixing area of a gasfired space heater employing pressurized combustor means. The pressurized combustor means include an elongate trough having an imperforate base wall and long side walls that are pierced by a plurality of pressurized combustion air inlet apertures, and a fuel gas supply conduit which extends generally longitudinally through the trough. The fuel gas supply conduit has a long surface that is pierced by a plurality of apertures through which fuel gas can enter the trough and be turbulently mixed with pressurized combustion air in a fuel gas-air mixing area, defined by the apertured trough side walls and the apertured fuel gas supply conduit surface, and can be ignited therein to produce an extremely intense heat source flame that is discharged into the space heater heat exchanger means via hollow interconnecting conduit means. The present invention preferably provides its novel pilot and main fuel gas supply means by installing partition means which divide the hollow fuel gas supply conduit into a pilot and a main gas supply potion. And, control and igniter means are also preferably pivoted in accordance with the present invention such that fuel gas will be first supplied to the mixing area via the pilot portion and ignited before any fuel gas is supplied via the main portion.

United States Patent Brandt et al.

[5 PILOT AND MAIN FUEL GAS SUPPLY MEANS FOR PRESSURIZED GAS- FIRED SPACE HEATER [72] Inventors: Theodore C. Brandt, Whitehouse,

Tex.; 'James L. Schulze, Sr.,

Middletown, Ky. [73] Assignee: General Electric Company [22] Filed: Nov. 30, 1970 [211 Appl. No.: 93,722

[52] US. Cl. ..431/43, 431/90, 431/180, 431/285 [51 1 Int. Cl ..F23q 9/08 [58] Field of Search ..431/42, 43, 47, 59, 264, 285, 431/90, 178-180 Primary Examiner-Carroll B. Dority, Jr. AttorneyFrancis H. Boos, Jr., Walter E. Rule and Frank L. Neuhauser 57 ABSTRACT invention provides novel means for supplying 51 Oct. 3, 1972 pilot and main fuel gas to the fuel gas-combustion air mixing area of a gas-fired space heater employing pressurized combustor means. The pressurized combustor means include an elongate trough having an imperforate base wall and long side walls that are pierced by a plurality of pressurized combustion air inlet apertures, and a fuel gas supply conduit which extends generally longitudinally through the trough. The fuel gas supply conduit has a long surface that is pierced by a plurality of apertures through which fuel gas can enter the trough and be turbulently mixed with pressurized combustion air in a fuel gas-air mixing area, defined by the apertured trough side walls and the apertured fuel gas supply conduit surface, and can be ignited therein to produce an extremely intense heat source flame that is discharged into the space heater heat exchanger means via hollow interconnecting conduit means. The present invention preferably provides its novel pilot and main fuel gas supply meansby installing partition means which divide the hollow fuel gas supply conduit into a pilot and a main gas supply potion. And, control and igniter means are also preferably pivoted in accordance with the present invention such that fuel gas will be first supplied to the mixing area via the pilot portion and ignited before any fuel gas is supplied via the main portion.

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PILOT AND MAIN FUEL GAS SUPPLY MEANS FOR PRESSURIZED GAS-FIRED SPACE HEATER CROSS-REF EREN CE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION This invention relates to means for supplying heat to a space, such as a room, house, building or the like and, more particularly, to novel means for supplying pilot and main fuel gas to the fuel gas-combustion air mixing area of a gas-fired space heater which employs pressurized combustor means including a fuel gas-air mixing area having sources of fuel gas and pressurized combustion air fluid-connected to it.

I-Ieretofore, conventional gas-fired space heater or furnace means have most frequently employed rather crude cast iron or steel heat exchanger means having the general shape of a hollow box or clam shell to transfer heat generated by the combustion of a combustible gas-air mixture to an air stream circulated between the heat exchanger means and the space to be heated. And, these conventional heat exchanger means have usually been combined with similarly unsophisticated combustor or burner means which have been very much like those used in gas cooking ranges and wherein the combustion air that is mixed with the fuel gas is supplied to the combustor means at atmospheric conditions. In these conventional space heater means, the atmospheric combustor means is located beneath the heat exchanger and the combustion products rise upwardly by natural convection through the heat exchanger and are discharged to the atmosphere via an exhaust vent or flue that is connected to the top of the heat exchanger.

The aforenoted copending, commonly assigned patent applications describe gas-fired space heaters which are superior to the aforedescribed conventional heaters in that they permit considerable weight and volume reduction in heat exchanger means material by employing a combination of highly efficient heat exchanger means for transferring heat to an air stream circulated between the heat exchanger means and the space to be heated, and pressurized high intensity combustor means for turbulently mixing fuel gas with pressurized combustion air to produce and ignite the combustible gas-air mixture.

The combustor means described in these aforenoted copending, commonly assigned patent applications include an elongate trough having an imperforate base wall and long side walls that are pierced by a plurality of pressurized combustion air inlet apertures, and a fuel gas supply conduit which extends longitudinally through the trough. The fuel gas supply conduit has a long surface that is pierced by a plurality of apertures through which fuel gas can enter the trough and be turbulently mixed with the pressurized combustion air in a fuel gas-air mixing area that is defined by the apertured trough side walls and the apertured surface of the fuel gas supply conduit. This turbulent mixture of fuel gas and pressurized combustion air can be ignited within the combustor fuel gas-air mixing area to produce an extremely intense heat source flame that is discharged to the inlet end of the heat exchanger means through hollow interconnecting conduit means. Typically, the intensity of this flame is at least 300,000 BTU of heat per hour per cubic foot of the interconnecting conduit means.

While the novel gas-fired space heaters described in the aforenoted copending, commonly assigned Abbott,

Boucher and Barnett patent applications are superior to the aforedescribed. conventional gas-fired space heaters, it has been found in accordance with the present invention that they can be still further improved by providing novel means for supplying pilot and main fuel gas to the fuel gas-air mixing area of the pressurized combustor means that they employ.

SUMMARY OF THE INVENTION This invention provides novel means for supplying pilot and main fuel gas to the fuel gas-combustion air mixing area of a gas-fired space heater employing pressurized combustor means including an elongate trough having an imperforate base wall and long side walls that are pierced by a plurality of pressurized combustion air inlet apertures, and a hollow fuel gas supply conduit that extends longitudinally through the trough and has a long surface that is pierced by a plurality of fuel gas inlet apertures through which fuel gas can enter the trough and be turbulently mixed with pressurized combustion air in a fuel gas-air mixing area defined by the apertured trough side walls and the apertured conduit surface. The present invention preferably provides its novel pilot and main fuel gas supply means by installing partition means within the hollow fuel gas supply conduit which is thus divided thereby into a pilot gas supply portion and a main gas supply portion. Control and igniter means are also preferably provided in accordance with the present invention such that fuel gas will be first supplied to the combustor means fuel gascombustion air mixing area via the pilot portion and ignited before any fuel gas is supplied via the main portion.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is illustrated in the accompanying drawings, wherein:

FIG. 1 is a somewhat schematic, partly sectioned, front elevational view of a space air-conditioning unit utilizing gas-fired space heater means incorporating a presently preferred form of the novel pilot and main gas supply means of the present invention;

FIG. 2 is an enlarged fragmentary sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a partly broken, greatly enlarged fragmentary sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a fragmentary sectional view taken along line 4-4 of FIG. 3; and

FIG. 5 is a schematic wiring diagram showing the electrical circuitry for the control means of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings and, more particularly, to FIG. 1 thereof, there is illustrated, somewhat schematically, an air-conditioning unit utilizing gas-fired space heater means 11 incorporating a presently preferred form of novel fuel gas supply means, generally designated 12 and shown in detail in FIGS. 3-5, provided in accordance with the present invention. The air-conditioning unit 10 is fluid-connected by right and left hollow conduit means 13 and 14 to a space 15 (shown in block), such as a room, house, building or the like, so as to condition air contained within the space 15, as by supplying heat to or removing heat from an air stream indicated by arrows 16, that is circulated between the space 15 and the air-conditioning unit 10 through the conduit means 13 and 14 by space air blower means 17. As shown, the air-conditioning unit 10 employs the gas-fired space heater means 11 to supply heat to the air stream, in combination with cooling means, including an evaporator section 18, to remove heat from the air stream 16.

As illustrated in FIG. 1, the air-conditioning unit 10 includes a generally rectangular hollow box-like cabinet 19 that is subdivided by a vertically arranged partition 20 into a left compartment 21 an a right compartment 22. The cabinet left compartment 21 has an air inlet opening 23 in its upper wall that is fluid-connected to the space 15 by the left conduit means 14, while the upper wall of the cabinet right compartment 22 has an air outlet opening 24 that is fluid-connected to the space 15 by the right conduit means 13. The cabinet left compartment 21 houses the cooling means evaporator section 18 and space air blower means 17, while the cabinet right compartment 22 houses the highly efficient heat exchanger means 25 and high intensity pressurized combustor means 26 that are combined to provided the gas-fired space heater means 1 1.

The gas-fired space heater means 11 is generally similar to that described in detail in the aforenoted copending, commonly assigned Barnett and Boucher patent application, except that the combustor means 26 is provided with the novel fuel gas supply means 12, which will be described in detail hereinafter.

As shown in FIGS. 1-4 the combustor means 26 includes an inverted, generally horizontally arranged, elongate trough 27 having an imperforate base wall 27b and generally vertically arranged, downwardly extending sidewalls 28 and 29 that are provided with a plurality of apertures along their upper and lower edges to respectively define primary combustion air inlet apertures 30 and secondary combustion air inlet apertures 31, having their central axes arranged generally horizontally. The upper surfaces of the inverted trough 27 are surrounded by a combustion air supply plenum 32 that is fluid-connected to a source of pressurized combustion air, such as a combustion air supply blower 33. The combustion air supply blower 33 includes an impeller 34 that is rotated by an electric motor 35 and is housed in the upper right hand comer of the cabinet right compartment 22 with its inlet connected to a combustion air intake conduit 36 which extends outwardly from the cabinet 19 through an opening 37 provided in the right side wall thereof. The combustion air supply blower 33 has its outlet fluid-connected to the combustion air supply plenum 32 via a combustion air blower discharge conduit 38 and a hollow box-like control chamber 39, which is similar to that described in detail in the aforenoted Barnett and Boucher patent application an and includes a similar damper 39d pivotally mounted within the control chamber 39 by hinge means 39h adjacent the connection of the combustion air supply blower discharge conduit 38 to the chamber 39 and an adjustable, normally open, electric control switch 39s which has an actuator 39sa interposed between the damper 39d and the combustion air supply plenum 32 of the combustor means 26 that is actuatable to closure by engagement by the lower portion of the pivotally mounted damper 39d.

As further illustrated in the drawings, an elongate, generally horizontally disposed, hollow-box like fuel gas supply conduit 40 extends generally longitudinally through the inverted trough 27 and has its long lower surface 41 pierced by a plurality of fuel gas inlet apertures that have their central axes arranged generally vertically and are located above the trough primary combustion air inlet apertures 30. These apertured trough side walls 28 and 29 and fuel gas supply conduit long lower surface 41 define a gas-air mixing area 42 for the pressurized combustor means 26 wherein fuel gas, such as natural gas, propane or the like, can be supplied via the gas supply conduit 40 and turbulently mixed with pressurized combustion air supplied via the trough combustion air inlet apertures 30 and 31 and ignited by igniter means, such as an electrically powered spark plug 43 mounted therein, to produce a generally downwardly extending, extremely high intensity heat source flame 44 (FIG. 2).

The present invention is particularly concerned with providing novel means for supplying fuel gas to the fuel gas-combustion airmixing area 42 of the combustor means 26 and igniting it therein. As is best shown in FIGS. 3-5, the present invention preferably provides integrated means for supplying both pilot and main fuel gas to the combustor fuel gas-air mixing area 42 by installing partition means 45 within the hollow box-like gas supply conduit 40, which is thus divided by the partition means 45 into a pilot portion 40p and a main portion 40m. As illustrated, the partition means 45 is mounted within the hollow fuel gas supply conduit 40 adjacent its right corner or end, such that the pilot portion 40p is fluid-connected to a first or pilot group of the gas inlet apertures 41p which pierce the fuel gas supply conduit long lower wall 41, while the main portion 40m is fluid-connected to a second or main group of the gas inlet apertures 41m which pierce the long lower wall 41 of the fuel gas supply conduit 40. The pilot 40p and main portions 40m of the fuel gas supply conduit 40 are fluid-segregated from one another by the partition means 45, and, preferably, the first or pilot group of gas inlet apertures4lp comprises approximately 10 per cent of the total number of all such fuel gas inlet apertures provided in the gas conduit long lower surface 41, while the second or main group of gas inlet apertures 41m comprises the remaining approximately per cent thereof.

In further accordance with the present invention, both the pilot portion 40p and the main portion 40m of the fuel gas supply conduit 40 are preferably fluid-connected to a common source 46 of fuel gas, such as natural gas, propane or the like. The pilot portion 40p is preferably fluidrconnected to this fuel gas source 46 via first piping means 46p including anormally closed, electrically powered first or pilot control valve 47p, while the main portion 40m is fluid-connected to this fuel gas source 46 via second piping means 46m, which include a normally closed, electrically powered second or main control valve 47m.

As illustrated in FIGS. 2-5 the electricallypowered spark plug or igniter means 43 is mounted generally horizontally within the right end of the combustor means fuel gas-combustion air mixing area 42 adjacent the first or pilot group of gas inlet apertures 41p, which pierce the fuel gas conduit long lower surface 41, at a point vertically spaced between the trough primary combustion air inlet apertures 30 and second combustion air inlet apertures 31. And, as best shown in FIG. 5, the solenoid 47ps of the normally closed, electrically powered first or pilot control valve 47p is electrically connected by conductor means 47' to power source lines L and L, in electrical series with the spark plug or igniter means 43 and the normally open damper actuatable control switch 39s and by conductor means 47" in electrical parallel with other electrical circuitry which includes the solenoid 47ms of the normally closed, electrically powered second or main control valve 47m that is in electrical series with normally open thermo-electric switch means 48 which include a bimetallic bridging contact member and is mounted within the combustor gas-air mixing area 42 adjacent the first or pilot group of fuel gas inlet apertures 41p and is adapted to close when it has sensed ignition of fuel gas admitted to the combustor gas-air mixing area 42 via the first or pilot group of inlet apertures 41p,

With the aforedescribed arrangement of the present invention, the gas-fired heater means 11 can be activated in the following manner. First, the combustion air supply blower 33 is started and the control switch actuator 39sa is adjustably positioned as described in detail in the aforenoted copending, commonly assigned Barnett and Boucher patent application, such that it is engaged by the damper 39d and pivoted to its closed position (FIG. 5) only just when the flow of the combustion air from its supply blower 33 to the combustor gas-air mixing area 42 is such that there will be optimum mixing in the area 42 between the combustion air and the fuel gas. Movement of the switch actuator 39sa to its closed position by the combustion air flow pivoted damper 39d will then simultaneously electrically connect the solenoid 47ps of the first or pilot control valve 47p and the spark plug or igniter means 43 across the electric power source lines L, and 1.12. thus opening the normally closed firstor pilot control valve 47p and admitting fuel gas to the combustor fuel gas-air mixing area 42 from the fuel gas source 46 via the first or pilot piping means 46p and the pilot portion 40p and first or pilot group of fuel gas inlet apertures 41p of the fuel gas supply conduit 40. The fuel gas which enters the right end portion of the combustor means gas-air mixing area 42 is next turbulently mixed with the pres surized combustion air that is admitted to the mixing area 42 via the adjacent primary combustion air inlet apertures 30 of the trough right end portion and this turbulent pilot mixture is ignited by the now-energized spark plug or igniter means 43, and is then further turbulently mixed with the pressurized combustion air that enters the gas-air mixing area 42 via the secondary combustion air apertures 31 which are located adjacent the first or pilot group of fuel gas inlet apertures 41 to produce a pilot portion of the total heat source flame 44 covering only about the rightmost 10 per cent of the downwardly opening trough mouth. Only after the ignition of this pilot mixture has been sensed by the switch means 48 and has thus caused its bi-metallic bridging contact member to close and thereby electrically connect the solenoid 47ms across the "electric power source lines L and I..,, will the normallyvclosed second or main control valve 47m be opened to allow admission of fuel gas to the combustor fuel gas-air mixingarea 42 from the fuel gas source 46 via the second or main piping means 46m and the main portion 40m and second or main group of fuel gas inlet apertures 41m of the fuel gas supply conduit 40. The gas thus admitted to the combustor fuel gas-air mixing area 42 via the second or main group of fuel gas inlet apertures 41m, which are, of course, located in a substantially common horizontal plane with the first or pilot group of fuel gas inlet apertures 41p, will then be ignited by the pilot portion of heat source flame 44, which has already been ignited by the spark plug or igniter means 43 as previously described.

As best shown in FIGS. 1 and 2,, the remaining structure comprising the air-conditioning unit 10 is generally similar to that described in the aforenoted copending, commonly assigned Boucher patent application. The highly intense heat from the flame 44, which extends across the entire length of the combustor gas-air mixing area 42, is now discharged from the lower or outlet end of the inverted trough 27 to an inlet at the upper end of the heat exchanger means 25 through the hollow box-like interconnecting conduit means 49. The intensity of the heat source flame 44 that is produced by the high intensity pressurized cornbustor means 26 is generally similar to that produced by the combustor means 36 described in the aforenoted Abbott patent application, and is typically at least 300,000 BTU per hour per cubic foot of the interconnecting conduit means 49, an intensity level far exceeding any previously achieved with the prior-art atmospheric combustion or burner means which have heretofore been commonly employed in conventional gas-fired space heaters.

The highly efficient heat exchanger means 25 comprises a plurality of generally vertically arranged hollow tubes 50. The tubes 50 have their upper ends fluid-connected in parallel to the lower end. of the interconnecting conduit means 49 provided between the bottom of the inverted trough 27 and the top of the heat exchanger means 25, while their lower ends are fluidconnected in parallel to an exhaust plenum 51 which directs the waste. products of combustion to an atmospheric exhaust vent means including an elbowshaped vent pipe 52 having an inlet leg 52a and an outlet leg 52b. The vent pipe inlet leg 52a is connected to the exhaust plenum 51 at the bottom of the heat exchanger means 25 and extends outwardly from the air conditioning unit cabinet '19 through an opening 53 provided at the lower end of the cabinet right side wall, while the vent pipe outlet leg 52b extends upwardly outside the cabinet. The vent pipe inlet leg 52a is sloped downwardly towards its intersection or elbow 52c with its upwardly extending outlet leg 52b, and liquid drain means 52d is provided at its lowest point, as at the bottom of the vent pipe elbow 52c.

Preferably, as in the case of the heat exchanger means described in the aforenoted Abbott patent application, the outer surfaces of the hollow tubes 50 of the heat exchanger means 25 are provided with fin means 54 of the so-called spine-fin type that are generally similar to those described in detail in the commonly-assigned prior art US. Pat. No. 2,983,300, except that the tubes and the fins for the "heat exchanger are preferably formed of a ferrous material, such as steel, rather than of a non-ferrous material, such as aluminum or copper as in the air-cooling exchanger described in US. Pat. No. 2,983,300.

As shown in FIG. 1, the space air blower 16 has its inlet 55 aligned with the air inlet opening 23 for the cabinet left compartment 21 and has its discharge 56 fluid connected to the right cabinet compartment 22 via an opening 56 that is provided in the partition 20, and is arranged such that rotation of its impeller 58 by its electric motor 59 will cause the air stream 16 to be circulated between the space 15 and the finned exteriors of the heat exchanger tubes 50. Hence, during operation of the combustor means 26 of the gas-fired space heater means 11, the right conduit means 13 serve as means for directing heated air from the airconditioning unit cabinet 19 to the space 15 or as the so-called warm air conduit means the left conduit means 14 serve as means for returning air from the space 15 to the air-conditioning unit cabinet 19 for the reception of heat or as the so-called return air conduit means, and the space air blower 17 serves as a means for circulating air between the space 15 and gas-fired heater means 11. Thus, during operation of the pressurized combustor means 26 of the gas-fired heater means 11, the combustion products resulting from the ignition and burning of the pressurized fuel gas and combustion air that are mixed in the fuel gas-air mixing areas 42 produce the highly intense heat source or flame 44, and they and the heat generated thereby are forced downwardly under the pressure provided by the combustion air supply blower 33 through the interconnecting conduit means 49 and tubes 50 of the heat exchanger 25, with the heat therefrom being transferred by conduction, convenction and radiation, first to the interiors of the tubes 50, then to the finned exteriors of the tubes 50, and finally to the space air stream 16 that is circulated across the finned exterior of the tubes 50 by the space air blower 17. And, the waste products of the combustion are forced from the lower ends of the heat exchanger tubes 50.and into the exhaust plenum 51 at the bottom of the heat exchanger 25, then outwardly and downwardly through the vent pipe inlet leg 52a and finally upwardly to the atmosphere via the ,vent pipe outlet leg 52b by the pressurized air supplied by the combustion air source blower 33. The rate of transfer of heat to the air stream 16 that can be accomplished by the heat exchanger means 25 is similar to that of the heat exchanger means described in detail in the aforenoted copending, commonly assigned Abbott patent application, and is typically at least 3,500 BTU of heat per hour per pound of material that is used in the tubes and the fins, a rate far exceeding any previously achieved with the aforedescribed rather crude prior-art box-like or clam shell-shaped heat exchangers which have heretofore been commonly employed in conventional, atmospheric gas-fired space heaters.

It should be apparent to those skilled in the art that while there has been described what, at present, is considered to be a presently preferred embodiment of this changes may be made to the disclosed apparatus without actually departing from the true spirit and scope of this invention. For example, the pilot and main gas portions of the fuel gas supply means might be formed separately from one another. It is therefore, intended that the appended claims shall cover such modifications and applications that may not depart from the true spirit and scope of the present invention.

What is claimed is:

1. In a gas-fired space heater employing pressurized combustor means including an elongated trough having an imperforate base wall and long side walls having therein a plurality of pressurized combustion air inlet apertures and a hollow fuel gas supply conduit that extends longitudinally through said trough and has a long surface containing a plurality of fuel gas inlet apertures through which fuel gas can enter said trough and be turbulently mixed with said pressurized combustion air in a fuel gas-air mixing area defined by said apertured trough side walls and conduit surface, integrated means for supplying both pilot and main fuel gas to said fuel gas-air mixing area, said integrated means comprising:

said hollow conduit; and partition means mounted within said conduit and dividing it into a pilot portion adjacent one end of said conduit and a main portion; said pilot portion including a first group of said fuel gas inlet apertures and said main portion including a second group of said fuel gas inlet apertures; igniter means mounted in said fuel gas-air mixing area adjacent said first group of gas inlet apertures;

and

control means for controlling the sequential admission of pressurized air into said trough, fuel gas to said pilot and thereafter fuel gas to said main portion such that fuel gas will be first supplied to said fuel gas-air mixing area at one end of said conduit via said first group of fuel gas inlet apertures and ignited by said igniter means before any fuel gas is supplied to said fuel gas-air mixing area via said second group of fuel gas inlet apertures.

2. The invention of claim 1, wherein said first and second groups of fuel gas inlet apertures are located in a substantially common plane.

55 3. The invention of claim 2, wherein:

a. said fuel gas inlet apertures have their central axes arranged generally vertically; and b. said pressurized combustion air inlet apertures have their central axes arranged generally horizontally and are vertically spaced from said apertured long surface of said hollow conduit. 4. The invention of claim 3, wherein: a. said trough is inverted; b. said apertured long surface of said conduit comprises its lower wall; and c. said pressurized combustion air inlet apertures are spaced below said lower wall of said conduit.

invention in accordance with the Patent Statutes, 

1. In a gas-fired space heater employing pressurized combustor means including an elongated trough having an imperforate base wall and long side walls having therein a plurality of pressurized combustion air inlet apertures and a hollow fuel gas supply conduit that extends longitudinally through said trough and has a long surface containing a plurality of fuel gas inlet apertures through which fuel gas can enter said trough and be turbulently mixed with said pressurized combustion air in a fuel gas-air mixing area defined by said apertured trough side walls and conduit surface, integrated means for supplying both pilot and main fuel gas to said fuel gas-air mixing area, said integrated means comprising: said hollow conduit; and partition means mounted within said conduit and dividing it into a pilot portion adjacent one end of said conduit and a main portion; said pilot portion including a first group of said fuel gas inlet apertures and said main portion including a second group of said fuel gas inlet apertures; igniter means mounted in said fuel gas-air mixing area adjacent said first group of gas inlet apertures; and control means for controlling the sequential admission of pressurized air into said trough, fuel gas to said pilot and thEreafter fuel gas to said main portion such that fuel gas will be first supplied to said fuel gas-air mixing area at one end of said conduit via said first group of fuel gas inlet apertures and ignited by said igniter means before any fuel gas is supplied to said fuel gas-air mixing area via said second group of fuel gas inlet apertures.
 2. The invention of claim 1, wherein said first and second groups of fuel gas inlet apertures are located in a substantially common plane.
 3. The invention of claim 2, wherein: a. said fuel gas inlet apertures have their central axes arranged generally vertically; and b. said pressurized combustion air inlet apertures have their central axes arranged generally horizontally and are vertically spaced from said apertured long surface of said hollow conduit.
 4. The invention of claim 3, wherein: a. said trough is inverted; b. said apertured long surface of said conduit comprises its lower wall; and c. said pressurized combustion air inlet apertures are spaced below said lower wall of said conduit.
 5. The invention of claim 4, wherein said first group of fuel gas inlet apertures comprises approximately 10 per cent of the total number of said fuel gas inlet apertures and said second group comprises the other approximately 90 per cent thereof. 